The present disclosure relates to microfluidic elements and, in particular, test elements for the optical analysis of a fluid sample with a substrate and a microfluidic channel structure that is enclosed by the substrate and a cover layer. The channel structure exhibits a measuring chamber with an inlet opening for the fluid sample.
In diagnostic tests (in vitro diagnostics), microfluidic elements are used to analyze a liquid sample and to thoroughly mix a fluid with a reagent. Body fluids are tested for an analyte contained therein for medical purposes. For this purpose, the fluid is mixed with a reagent, for example a liquid reagent. If the reagent is a solid, it is dissolved and homogenized by the fluid.
Measuring chambers of this type constructed as detection cuvettes are known. They are preferably inserted into rotary test elements or centrifugal test carriers (disks). The necessary steps of a method are carried out in the fluid structures of the test elements in order to carry out the appropriate reactions to detect an analyte in a fluid.
Both rotary and also non-rotary test carriers or test elements each have a microfluidic channel structure to accommodate a fluid sample. The channel structures often comprise a plurality of chambers so that complex, multi-step test procedures (test protocols) can be carried out. Such test carriers, as a rule, have at least one, frequently a plurality of fluid channel structures so that a plurality of tests can be carried out in parallel.
In so-called dry chemical test elements, the reagents required for the tests are initially introduced into the reagent chamber in the liquid form and dried therein. The reagent is normally dissolved using the fluid sample. After dissolving and thorough mixing in order to produce a homogeneous fluid sample, the mixed fluid is directed via further channels from the reagent and mixing chamber into an analysis or measuring chamber, where evaluation of the fluid sample takes place in order to detect and determine a specific analyte in the sample.
The sample fluid reacts with the reagent in the test element, resulting in a change in a measured parameter that has a definite relationship with the test analyte. This change in the measured parameter is measured in the test carrier itself. In addition to electrochemical evaluation methods, optical evaluation methods are routine, in which a change in color or other optically measurable parameter is detected.
There is a need in the art for test carriers that, before the measurement, mix the sample fluid as homogeneously as possible with the desired reagents. At the same time, the test elements and microfluidic channel structures employed are becoming ever more compact in order to produce as many parallel channel structures as possible on one test carrier.